1. Field of the Invention
The present invention relates to checkout systems and more particularly to a checkout counter having sensing means for controlling the reading of coded labels attached to merchandise items during a checkout operation.
2. Description of the Prior Art
In order to increase the speed of the checkout operation, optical scanning devices have been incorporated into checkout counters for reading data encoded indicia on labels affixed to the purchased merchandise items. Movement of the merchandise items past the scanning device results in the scanning device reading the encoded indicia labels. To control the operation of the scanning device, detecting means have been positioned in the path of movement of the merchandise items to operate the scanning device in accordance with the position of the merchandise items with respect to the scanning device. Thus, a first or enter detector gate positioned upstream of the scanning device will turn on the scanning device for operation upon detecting the presence of a merchandise item upstream of the scanning device, while a second or exit detector gate located downstream of the scanning device will turn the scanning device off upon detecting the presence of the merchandise item downstream of the scanning device. Typically, the item gates are mounted in a structure located adjacent the scanning device and at a position above the level of the top surface of the checkout counter. Examples of this type of structure may be found in U.S. Pat. Nos. 4,086,476, issued to R. King, and 4,575,623, issued to V. Cononi, both of which are assigned to the assignee of the present invention. Where the installation requires that the checkout counter have a completely free top surface, the item gate structure disclosed in the above cited patents could not be used. Without the use of item gating, multiple read errors, as well as laser radiation overexposure, become problems.
The background art known to the applicants at the time of the filing of this application is as follows:
U.S. Pat. No. 3,946,224, Method And Device For Detecting The Passage Of Objects, by J. Allera et al.;
U.S. Pat. No. 4,317,992, Object Detecting Apparatus, by N. Stauffer; and
U.S. Pat. No. 4,329,581, Ambient Light Sensor Touch Switch System And Method, by R. C. Helfrich, Jr., et al.